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    <script>

        // 1.forEach循环
        var arr = ["张三","李四","王五"]
        arr.forEach(function(item, index, arr) {
            console.log(item, index, arr)
        })
        // 定义myForEach函数
        function myForEach(arr, fn) {
            for(var i=0; i < arr.length; i++) {
                fn(arr[i], i, arr)
            }
        }
        

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